Thank you for your feedback, I definitely understand where you are coming from. Perhaps player speed could be adjustable or yeah multiple portals could have been used. The thing with multiple portals at once is it makes the controls slightly less intuitive than with just one portal.
Another idea perhaps is a slowdown mechanic where the player can move slower for a few seconds at a time to give them more time to think and figure out the puzzle while still having the time constraint of the player moving forward.